It is known to stabilize a spine having damaged vertebrae by implanting a stabilizing system in the vertebrae on either side of a damaged vertebra. For this, the spine is first set and then stabilized. It is further generally known to turn so-called pedicle screws into the pedicles of vertebrae and to connect the pedicle screws to each other through a more or less rigid connecting system. For example, this can be obtained by using a so-called distracting or compressing bar which is inserted in a receiving slot provided in the heads of the pedicle screws. The bar is usually provided with a thread, a grooving or some other surface roughness such that it can be fixed in the head of the pedicle screws by means of an appropriate locking means. EP 0 348 272 discloses a pedicle screw having a receiving slot which is provided with a thread to receive a locking screw. The locking screw fixes the distracting or compressing bar in the slot. U.S. Pat. No. 4,763,644 discloses a pedicle screw, the head of which is provided with an outer thread onto which a cap-shaped nut can be screwed. By means of a pin portion inserted into the receiving slot, the cap nut urges the bar against the bottom of the receiving slot. French patent 26 24 270 discloses a cap nut including a locking screw to fix the distracting or compressing bar in the receiving slot. Cap nuts have the advantage of holding together the legs of the slotted pedicle screw head. As mentioned above, there is a danger that the legs may spread apart, thus loosening the locking screw when a solid screw is screwed into the receiving slot. Furthermore, fixing of the distracting bar is risky. In the process of the operation, the pedicle screws are first secured. The position of the pedicle screws (or, respectively, the heads thereof) is optional to some extent, in particular, when the vertebrae are more or less displaced. According to the prior art it is required to prebend the distracting or compressing bar to be received in the receiving slots of the pedicle screws. Since the distracting and compressing bars must be stiff by nature, the process described requires the surgeon to apply substantial efforts, and the process is complicated.
An object of the present invention is to provide a device for setting a spine having damaged vertebrae so that there is reduced need for bending a distracting or compressing bar when the bar must be received and fixed in receiving slots of anchoring elements secured to the vertebrae when displaced vertebrae exist.
This object is solved by the device of the invention.